Toward Reliable Uptake Metrics in Large Vessel Vasculitis Studies

Area of Science:

• Nuclear Medicine
• Radiology
• Immunology

Background:

• Large vessel vasculitis (LVV) is a serious condition affecting major arteries.
• Accurate assessment of inflammation in LVV using FDG-PET/CT is crucial for patient management.
• Understanding factors influencing blood pool activity in FDG-PET/CT is essential for reliable image interpretation.

Purpose of the Study:

• To investigate the impact of sex, age, fat mass, fasting blood glucose level (FBGL), and estimated glomerular filtration rate (eGFR) on blood pool activity in LVV patients.
• To determine the optimal metric (SUV or SUL) for assessing blood pool activity in LVV.
• To provide guidance on interpreting FDG-PET/CT findings in patients with varying physiological parameters.

Main Methods:

• Analysis of 41 FDG-PET/CT scans from LVV patients.
• Measurement of blood pool activity in the superior caval vein using standardized uptake values (SUVs) and standardized uptake values lean body mass (SULs).
• Statistical analysis including t-tests for sex differences and correlation analyses for age, fat mass, FBGL, and eGFR.

Main Results:

• Women exhibited significantly higher SUVs compared to men, while SULs were comparable between sexes.
• Increased fat mass correlated with higher blood pool SUVs but not SULs.
• Lower eGFR was associated with elevated FDG blood pool activity across all uptake metrics.

Conclusions:

• Standardized uptake values lean body mass (SUL) is recommended over standardized uptake values (SUV) for assessing blood pool activity in FDG-PET/CT studies of LVV patients.
• Caution is advised when interpreting SUV and SUL measures in patients with impaired kidney function.
• Sex and body composition (fat mass) influence SUV measurements, highlighting the importance of using lean body mass-corrected values.